Control of record media using device only accessible control areas and directory of media control marks and error history

ABSTRACT

A data storage system includes a data storage medium, such as a magnetic tape, that has a first control data storing area or drive partition that is addressable only by a peripheral drive mounting the medium and a plurality of other addressable data storing partitions for storing data. A volume table of contents may be stored in one of the addressable partitions. A tachometer measures and indicates physical locations on the storage medium. Each of the partitions have an extent on the storage medium indicated by said physical locations. The control data in the drive partition includes directories of medium control blocks, such as tape marks, defect marks and the like; directory of all addressable partitions including the physical locations at the beginning of each partitions and other medium physical and logical parameter data. A so-called mount-demount medium control block in the drive partition indicates a demount status that shows all data stored in the drive partition is valid. Loading a storage medium into a drive does not mount the drive for recording and reading. First, a copy of the drive partition stored data is copied to a memory in the peripheral drive and the mount-demount medium control block is marked to indicate the storage medium is mounted. Then, the peripheral drive can indicate to an attaching unit that the storage medium is mounted for use in data processing activities.

DOCUMENT INCORPORATED BY REFERENCE

Milligan et al U.S. Pat. No. 4,393,445 is incorporated by reference intothis application for patent.

FIELD OF THE INVENTION

This invention relates to data storage devices including control ofrecord media by a device independently of attaching host processors andthe like.

BACKGROUND OF THE INVENTION

Prior data storage subsystems required host processor intervention indata storage subsystem operations for performing high speed searches(tape head is not in contact with the tape that is moving faster thantape speed during reading or writing), scanning a record medium (a slowspeed search wherein the head is in transducing contact with the tapefor reading block ID's, for example), particularly a magnetic tapemedium, until a desired logical block is located on the record medium.This situation creates undesired performance problems in those datastorage systems employing record media that store an order of magnitudemore data than prior art record media. Eliminating or reducing the priorart required host intervention in other aspects of data storagesubsystems also increases the efficiency of host processor operations inthat attention needed to operate with data storage subsystem operationshas been eased.

DISCUSSION OF THE PRIOR ART

The prior art provided a directory in each record media that is created,updated and managed by software in a host processor attached to a datastorage subsystem. One representative example of such a directory isshown by Kulakowski et al in U.S. Pat. No. 4,939,598. A volume table ofcontents (VTOC), another name for a directory recorded on a recordmedium, for an optical disk file is created, updated and managed by anattaching personal computer, a low performance host processor. Such VTOCincluded status of addressable data-storage areas on the optical diskdata storage medium. Other prior art data storage systems employ similartechniques. Such record medium stored directories typically includedaddressing capability requiring a host processor to execute softwarethat addresses a medium, rather than allowing a data storage subsystemto address internal data structures of a record medium independently ofhost processor software. It is desired to remove dependency ofaddressing internal data structures of a record medium from hostprocessor executed software. An example representative of suchaddressing directories is shown in Kulakowski et al U.S. Pat. No.4,575,827. Magnetic tape record media also often included host created,updated and managed records that enabled host processor software toaccess records stored in a magnetic tape volume. As stated in Kulakowskiet al, such control records were termed "tape table of contents", TTOC,rather than VTOC.

Even the addition of so-called "virtual volumes" or "logical volumes"did not remove the requirement for host processor executed software fromcreating, updating and managing internal data structures of such virtualvolumes. Clifton et al in U.S. Pat. No. 4,310,883 shows host processorsaddressing data in a mass storage system using virtual volumes andvirtual devices. While the mass storage subsystem matched the virtualvolumes to physical tape volumes, host processor executed software stillmanaged the internal data structures of such virtual volumes. There wasno mass storage system created, updated and managed control other thanmatching the virtual volumes to physical volumes. Clifton et al citeU.S. Pat. No. 3,670,307 as a showing of virtual volume addressing byhost processor software using a logical address base.

Duke et al in U.S. Pat. No. 4,429,363 show a cached DASD data-storagesubsystem. Content control indica in the Duke et al cache includes whatis often referred to as a "written to" bit or a "modified bit". Whensuch a bit (M 66 in Duke et al) is active (usually unity), then theaddressable data storage area has been written or modified while wheninactive (usually zero) it indicates congruence with a copy stored inthe backing store. The purpose of such a written to bit is to avoidcopying data from the cache to the backing store if both copies areidentical. Duke et al cite U.S. Pat. No. 3,588,839 that teaches that awritten to bit is used to control copying data from a front store to abacking store. That is, only that data that is not written to is copiedfrom a front store (cache) to a backing store that is not congruent withthe backing store. Duke et al also use the written to bit to avoidpromoting or staging data from the backing store to the front store ifthe copies are congruent. The Duke et al backing store can be consideredas an archive for the cache stored data. Therefore, the written to bitalso indicates whether or not data are to be archived, such as in apartial archive of data stored in any data storage device.

SUMMARY OF THE INVENTION

The present invention provides a peripheral device (hereinafter drive)addressable area (herein device partition) that is not addressable byhost processor software that enables the peripheral drive to create,update and manage directories and other volume-related data structureswith respect to data stored in a data storage volume. Such datastructures are data block map (hereinafter DBM) that addressablyidentifies not only host processor addressable data blocks but subsystemdata blocks that may or may not be addressable by an attaching hostprocessor. Such DBM enables a peripheral drive to execute high speedlocate for rapidly finding a host processor addressable data block or aperipheral drive or drive only addressable data block. Physical mediumlocations are identified in the DBM. That is a peripheral drive, such asa magnetic tape drive has a reel tachometer indicator that metersmagnetic tape displacement for providing tape displacementaddressability of a magnetic tape that facilitates high speed searchingor locating data blocks. A plurality of reference physical locations orpoints are established for facilitating high speed (tape movement thatis not in contact with a head). Such locations are not identified on thetape, per se, rather are measured and indicated by a suitable tapedisplacement meter, such as a reel tachometer.

In another aspect of the invention, the status of the DBM and of thephysical volume is indicated in the peripheral drive only addressablearea. Such status is useful for removable media. The status for aremovable medium is either mounted or demounted as indicated in amount-demount indicator block (MDI). Such status also indicates whetheror not the DBM has been logically "checked out" or removed from therecord medium, i.e. if a record medium is mounted, then only a drivecopy of the DBM is valid. A record medium may be loaded into aperipheral drive but not have a mounted status. Similarly, a fixedmedium may not have a mounted status. Mounted status in a peripheraldrive requires that a separate copy of the DBM be stored within theperipheral drive that is not on the record medium to which the DBMpertains. Such separate copy may be stored in a RAM. The peripheraldrive changing the record medium status from mounted to demounted(whether or not the record medium is to be removed from the peripheraldrive) validates the copy(s) in the record medium. Loading a recordmedium into a peripheral drive having the mount status indicates to theperipheral drive that the DBM is not valid.

A directory of peripheral drive readable "end-of-data" (EOD) data blockor tape marks enables high speed locate to the last written EOD thatsignifies the end of data of a record medium. Other EOD blocks are usedto high speed locate to end of data in so-called partitions in amagnetic tape.

Externally identified (viz by a reel tachometer or a magnetic disktachometer) physical locations identify so-called partitions in a recordmember. High speed locate access to such partitions is enabled by adirectory of such partitions.

A plurality of said DBM's and MDI's are recorded in the driveaddressable area. Each DBM copy has an associated MDI copy such that ifonly one of many copies is valid, a peripheral drive can still employ,update and manage the DBM.

A peripheral drive constructed using the present invention verifies upona mount request that a loaded record medium has a valid copy of its DBM.The peripheral drive does not respond with a mounted message to arequesting host processor until after a valid copy of DBM is copied intothe peripheral drive and all of the MDI's on the record medium arerecorded as showing the record medium is mounted.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings.

DESCRIPTION OF THE DRAWING

FIG. 1 illustrates in simplified block diagram form a data processingsystem in which the present invention is employed.

FIG. 2 is a simplified partial showing of a magnetic tape having aformat employing the present invention.

FIG. 3 is a diagrammatic partial showing of track wraps on the FIG. 2illustrated magnetic tape format.

FIG. 4 is a simplified showing of data structures used to illustrate thepresent invention.

FIG. 5 is a simplified flow diagram relating to mounting a FIG. 2illustrated tape for illustrating peripheral drive operations employingthe present invention

FIG. 6 is a simplified flow chart showing peripheral drive operationswhile the FIG. 2 illustrated magnetic tape is mounted in a peripheraldrive.

FIG. 7 is a simplified flow chart showing a high speed locate using thepresent invention.

FIG. 8 is a simplified flow chart showing a high speed location of lastdata recorded on the FIG. 2 illustrated magnetic tape or a partitionthereof.

FIG. 9 is a simplified flow chart showing selection of a tape motion foraccessing an identified data block in the FIG. 2 illustrated magnetictape or in a partition of the magnetic tape.

FIG. 10 is a simplified flow chart showing demounting a FIG. 2illustrated tape from the FIG. 1 illustrated data processing systemwithout immediately unloading the magnetic tape from the peripheraldrive.

FIG. 11 is a simplified flow chart showing formatting a tape andcreating partitions in the FIG. 1 illustrated system.

DETAILED DESCRIPTION

Referring now more particularly to the appended drawing, like numeralsindicate like parts and structural features in the various figures.Referring first to FIG. 1, a tape drive 10 is connected (attached) toother units 12 via peripheral controller 11. A direct connection withoutcontroller 11 is also contemplated. Other units 12 represent computersof all types, communication systems, local networks and the like. In aconstructed embodiment, a tape cartridge 17 containing a single spool 20of magnetic tape 21 is removably inserted into tape drive 10. Tapecartridge 17 shown in a play position operatively connects a spool motorand tachometer 22 to tape spool 20 for unreeling and reeling tape 21.Tape 21 is automatically threaded (in a known manner) pastlaterally-positionable multi-track multi-gap head 27 to machine reel 25.Data are transferred between tape 21 and other units 12 via data flow28. Data flow 28 performs the usual formatting, error detecting andcorrecting, and other processing of information-bearing signals (data)found in magnetic tape recording apparatus. Motor and tachometer 26rotate spool 25 in synchronism with spool 20, as is known. Lines 23denote control and sensing signal transfer between motors 22 and 26 withtape drive control 30. Control 30 includes the usual programmed controlfor controlling data flow 28 and communicating with other units 12.Cartridge present sensor 31 senses the cartridge 17 for informingcontrol 30 that cartridge 17 has been loaded into tape drive 10. Randomaccess memory (RAM) 33 buffers data for data flow 28, stores controlinformation for control 30 and may store an operating program forprogrammed control 30. Of course, control 30 may employ a read onlymemory (ROM) (not shown) for containing its program elements. Ofinterest to the present invention is the storage of a separate copy ofthe Data Block Map (DBM) 34 and a separate copy of a statisticalanalysis recording system (SARS) 35 in RAM 33. These item 34 and 35 arealso stored in tape 21 in a portion that is addressable only byperipheral drive 10, as will become more apparent.

Referring next to FIGS. 2 and 3, the tape track format, servo format,DBM and SARS storage on tape 21 and the like are described. Tape 21includes triple longitudinally-extending laterally-spaced-apartredundant identical longitudinally-extending servo areas 40-42 forlaterally relatively position tape 21 and head 27 in four relativepositions. At a free end of tape 21 (to the left in FIG. 2), a drive totape calibration area is disposed between dashed lines 50 and 52. Thisarea contains signals (not described) that enable tape drive 10 tocalibrate its operation to the particular characteristics of the loadedtape 21. The tape area between dashed line 52 and a hub end of tape 21is available for recording. The later described track groups 0-3respectively have a beginning of wrap (BOW) tape control block (notshown) longitudinally adjacent dashed line 52 and a end of wrap block(EOW) 59 at the hub end near line 56. Dashed lines 54 respectivelyindicate addressable logical partitions each of which is a collection ofcontiguous sectors that are indicated and addressed using tachometer 22.As will become apparent, such dashed lines can either denote suchtachometer 22 indicated tape displacement locations for all data tracksor for only selected data tracks. In the latter regard, numeral 58denotes four track groups 0-3 used in a constructed embodiment and asbest seen in FIG. 3. Serial recording proceeds from track group 0through track group 3, no limitation thereto intended. The dashed line54 indicated displacement locations preferably relate to tracks only inthe respective track groups 0-3. Track portions between longitudinallyadjacent ones of the dashed lines 54 are partitions. Dashed line 56indicates approaching the hub end of tape 21. In each of the trackgroups, line 56 may be at a different longitudinal position. Forexample, if a medium defect X is longitudinally adjacent the hub end oftape 21 affects data tracks in track groups 0 and 2 but not 1 and 3,then a end of wrap data block EOW 59 (later described) is recorded ingroups 0 and 2 tracks for shortening the data track lengths while anidentical end of wrap block EOW 59 is written in track groups 1 and 3 atdashed line 56. Detected media defects remote from either longitudinalend of tape 21 are identified by a pair of so-called servo defect blocks(SDB), tape control blocks, that respectively are immediately upstreamand downstream from the detected defect for defining a limited portionof a group of data tracks in one of the track groups 0-3 that is notavailable for recording because servo areas 40-42 are affected by themedium defect.

First track group 0 is laterally displaced from longitudinal edges 57respectively by tracks in track groups 3 and 1,2. Since track group 0 isa logical beginning of data recording, tape control information (DBM andSARS) is recorded in track group 0 in a so-called drive partition thatexists between dashed lines 52 and a first dashed line 54. Such drivepartition in track group 0 is only addressable by tape drive 10 and notby controller 11 nor other units 12. All other-units addressablepartitions on tape 21 are arbitrarily numbered from 0 to a currentmaximum number of partitions. Each partition, whether a drive partitionor an addressable partition, is a logical collection of contiguoussectors, each partition may have a different number of sectors. A sector(sometimes referred to as a segment) is a tachometer 22 determinedlength of tape and can be accessed by moving tape 21 and monitoringtachometer 22 generated count values (not shown). Any form of physicallocation addressing may be used, such as arbitrarily selected tachometercount values. First dashed line 54 does not apply to data tracks intrack groups 1-3. Milligan et al in U.S. Pat. No. 4,393,883 showsgenerating physical reference values (PRV) that are usable to identifythe sectors on tape 21.

Control information stored in the drive partition is useful tocontroller 11, other units 12 or tape drive 10 but such controlinformation is addressable and readable only by peripheral drive 10.Tape drive 10 may supply such information to either controller or otherunits 12, as may be desired. The control information stored in the drivepartition is that information primarily useful to tape drive 10 as itidentifies physical locations on tape 21 of diverse control dataelements useful for quickly locating data stored on tape 21, thereforeit is referred to as storage medium physical access data. The usualprior art VTOC or TTOC may be stored in partition 0 for identifying toother units 12 the informational content of tape 21 including thelogical data elements as partitions, logical volumes, files and thelike. Control information shown in FIG. 2 identified by numerals 60-78,in the drive partition is not visible (addressable) outside of tapedrive 10. The illustrated drive partition may consist of a plurality ofpartitions, for example, a DBM partition for storing all copies of DBM,a SARS partition for storing all copies of SARS and a MDI partition forstoring all copies of MDI. All other partitions are addressable,explicitly or implicitly by other units 12. Implicit addressing is byother units 12 addressing files, virtual volumes and the like. Tapedrive 10 has the usual load point controls for positioning magnetic tapeand magnetic head 27 to first read the tracks in track group 0.

Control information in tape drive 10 created, updated and managedpartition includes a format identification (FID) block 60 (FIG. 4). FID60 indicates that tape 21 is formatted as shown. All other controlinformation is stored in K copies, K is an integer preferably 2^(J)where J is a positive integer, such as 3. Each block of controlinformation is separated by a usual interblock gap (IBG) 61. A firstcopy of the control information includes mount-demount indicator MDIblock 63, copy 1 indicated by MDI 1, DBM 1 (copy 1 of K) and SARS 1(copy 1 of K). All additional copies of the control information arerepresented by ellipsis 74. An end-of-data EOD tape control block 78indicates the end of data in the tape drive accessed partition indicatedby numeral 75. MDI 1 may be stored in the drive partition after SARS 169, i.e. between SARS 1 and EOD. Alternately, all MDI copies may bestored in one string of blocks, all DBM copies stored in a second stringof blocks and all SARS copies stored in a third string of blocks. Thesequence of storage in the drive partition is one of choice.

FIG. 3 diagrammatically illustrates obtaining a maximal spacing betweenadjacent data tracks in each track group 0-3. Numerals 81-89respectively indicate track clusters 1-8, and remaining track clusters,each track cluster having one track from each track group 0-3. Laterallyadjacent track clusters have tracks scanned in opposite scanningdirections 79 and 80. Magnetic tape 21 moves in a direction to the trackscanning direction by magnetic head 27. The "to hub" scanning directionis caused by magnetic tape 21 being reeled from cartridge spool 20 whilethe "from hub" scanning direction is caused by magnetic tape beingreeled onto cartridge spool 20. Magnetic tape 21 is scanned in aserpentine sequence. While magnetic head 27 is at one lateral (index)position, one serpentine scan (also termed a track wrap) occurs. In scandirection 79 one track in each of the odd numbered clusters are scannedwhile in scan direction 80 one track in each of the even numbered trackclusters are scanned. The arrows in the respective track clusters 81-89(numbered as clusters 1-8 plus remaining clusters) indicate the tracks.Each vertical number sequence "2 0 1 3" in each of the track clustersrespectively indicate the track group to which the respective data trackbelongs. The track number of the arrow indicated tracks in each of theclusters is determined by the following equations wherein K is thecluster number from 1-32:

    Track number of track group 2 track=(K * 4)-3              (1)

    Track number of track group 0 track=(K * 4)-2              (2)

    Track number of track group 1 track=(K * 4)-1              (3)

    Track number of track group 3 track=(K * 4)                (4)

In each data track area 45-48, in a constructed embodiment, all of thetracks are evenly spaced apart laterally, no limitation theretointended. The concurrently accessed tracks of each track group arespaced apart by seven intervening tracks. For example, tracks 1 and 9,as determined by the equations above, are laterally separated by tracks2 through 8. For having four groups of tracks, such lateral spacing ismaximum for all tracks and is the same for all successively numberedtracks in each track group. Note that the tracks of track group 2 in theeven numbered track clusters are not accessed concurrently to the trackgroup 2 tracks in odd numbered clusters. Also, the four data track areas45-48 (FIG. 2) have a like number of tracks (each data track area haseight track clusters) such that the servo track areas 40-42 have amaximum lateral spacing. Such maximum lateral spacing is an optimumspacing for reducing errors caused by magnetic tape defects. A pair ofunrecorded longitudinally-extending guard bands 43 separate the datatrack areas from each of the servo track areas 40-42.

Numerals 54-A and 54-B respectively indicate different partitionboundaries of a partition disposed adjacent the hub end of tape 21 andthat spaces the EOW block 59 indicating end of wrap. Such partitions mayalso span BOW tape control blocks and extend between adjacent trackgroups. That is, a partition can begin in track group 0 and extend intotrack group 1. Also a partition can include the entirety of tape 21recording area except for the drive partition. In scan direction 79numeral 54-A indicates P's denoting location in each of the data tracksof track group 1 in an odd numbered cluster that is a partition leadingboundary (first scanned in a forward direction of tape motion).Similarly, numeral 54-B indicates an end of such partition in trackgroup 1 but occurring in even numbered track clusters in scan direction80. Such partition boundaries contain no special marks, that is, suchboundaries are addressed by tape displacement. Alternately, apartition-boundary-indicating tape control block may be used. In theformer embodiment, data blocks, as in the prior art, are addressed byother units 12 using block ID's.

As used herein, the term forward direction means the direction of trackscanning for writing data. Track scanning in a reverse direction istermed a backward direction. Tape 21 is transported between reels 20 and25 in a reciprocating manner but the track scanning is in a forwarddirection or backward direction irrespective of actual tape direction ofmotion. The terms "upstream" and "downstream" defining an item on tapewith respect to a current tape position to respectively mean that anitem is scanned either before or after said current position in theforward direction of scanning.

FIG. 4 illustrates all of the data structures used herein. DBM 34,whether stored in RAM 33 or tape 21, has VOLID field 90 storing thevolume ID or VOLID of the physical tape volume. The directories and mapsin DBM 34 as described below include linked lists of a plurality ofentries in the respective directories and maps. A pair of pointers pointrespectively to the beginning and end of each of the linked lists. Suchlists can be singly or doubly linked. Tachometer count values in eachdirectory indicate the respective tape displacement location in aforward direction of data track scanning. Tape lengths betweensuccessive tachometer counts are termed sectors. A partition is anaddressable logical collection of contiguous sectors. Block ID's andother logical data indications may be included in any of the directoriesand maps. Partition directory 91 includes the forward direction tapedisplacement tachometer location of each partition along with a block IDidentification of a first logical block in each partition. Thepartitions are enumerated in any numerical sequence, preferably fromzero to a highest current numbered partition. The tape drive reservedpartition between dashed lines 52-54 is not included in directory 91 asit is not addressable by other units 12. Both the sector and partitionnumerical sequences begin at the load point or beginning of track group0, then proceed to the end of track group 0, thence to groups 1, 2 and 3(in that order) such that the forward direction of scanning appears asone long tape medium, as indicated in FIG. 3. Data tracks in evennumbered track clusters in each track groups are scanned first,therefore have lower tachometer count values than data tracks in oddnumbered track clusters. Changing the accessible length of data tracksby moving EOW block in front of a defect X (FIG. 2) does not change thetachometer tape displacement count as the defect is scanned over whetheror not data are recorded in the track group affected by such defect.

Tape mark directory 92 indicates the sector number of each tape mark ontape 21. Tape marks in the prior art were special recorded patterns fordefining data file boundaries on data-storing magnetic tapes. In thedescribed embodiment, such tape marks still indicate data fileboundaries but are recorded as a later described tape control block. Thetape mark directory is useful in connection with determining data filelimits on tape 21 for selecting a tape moving algorithm as shown in FIG.9.

Servo demark directory 93 includes tachometer indications of locationsof servo demark tape control blocks. Such demark tape control marks arelink listed together in respective demarked media defect areas as laterdetailed.

Logical volume directory 94 indicates the partitions having logicalvolumes and the tachometer number indicating location of each suchlogical volume. Logical volumes are addressable by other units 12 as ifsuch logical volume was a physical volume. Such logical volumes containtheir own respective block ID sequence that is independent of the blockID sequence used in the physical tape volume not included in suchlogical volume. Directory 94 may also contain other data particularlyrelating to logical characteristics of such logical volume. Tape drive10 writes an EOD tape control block in each partition for indicating endof data recording. An empty partition optionally has an EOD block at itsbeginning location. Such EOD block, even when in a logical volume thatoccupies one or more partitions, is included in directory 91.

Wrap point map 95 identifies the track hub end extremities of datatracks measured in the forward direction and the respective mid pointsof the data tracks. That is, map 95 identifies the tachometer count foreach EOW block 59 (data track extremity near the hub) for all datatracks in even numbered track clusters respectively in each track group.Map 95 also includes identification of a plurality of other physcialreference points that are tachometer identified, such as track midpoints, and the like.

Defining map 95 in another way, each physical reference pointidentification can also be deemed to include a quarter-point of eachtrack group. Other track arrangements result in differing arrangementsfor the reference points. Also, if one terms a track group a wrap of oneset of data tracks, then all tracks in a track group in even numberedtrack clusters are deemed to be a first half-wrap and all data tracks ofthe track group in the odd-numbered track clusters are a secondhalf-wrap. Wrap point map 95 includes a so-called mid-pointidentification is the midpoint of each wrap. Field 96 indicates the typeof physical volume, such as capacity, number of track groups, etc.

Directory 97 includes a linked list of EOD block sector locationslogically listing the EOD's from tape load point to the end of trackgroup 3. A pair of pointers respectively point to a first EOD and a lastEOD. The last EOD enables a fast locate to the end of recorded data ontape 21.

Format identification block 60 (ignoring the usual tape clocksynchronization field, etc) includes the tape 21 volume identificationVOLID 100, track data 100 and other format identifying data 102. Thetrack data 101 include number of data tracks, track cluster and groupdefinitions, sector length or extent definitions and the like. Otherdata 102 may include logical definitions, such as logical volumerestrictions, volume affinity parameter data (i.e. relationships toother volumes) and the like.

Tape control block 78 includes the usual clock and byte synchronizationsignals 111. Header 112 may include an identification of type of tapecontrol block, i.e. tape mark, EOD, BOW, EOW, servo defect block (SDB)and the like. Header 112 also may include a block ID of the tape controlblock. The sequence of data block "block ID's" is a separate sequencethan that used for tape control blocks. Other data beyond thisdescription may be included in field 113. Error detecting and correctingECC field 114 contains suitable error redundancy data. If reading ispermitted in a track scan direction opposite to the forward scanningdirection, then postamble 115, a mirror image of preamble 111, ends tapecontrol block 78. If reading is permitted only in the forward direction,then postamble 115 is replaced by a terminating or trailer of anyconfiguration.

SARS 35, by way of example, includes field 105 that indicates the numberof bytes of data read and recorded from and to tape 21 along withsuitable time stamps (dates). All write errors are logged in field 106.Similarly, read errors (even ECC corrected read errors) are logged infield 107. Field 108 stores a history and sector locations of detectedmedia defects. Field 101 stores a history of calibration errorsresulting from calibrating tape drive 10 using area between dashed lines50 and 52. Other error and statistical data are included as desired.

FIG. 5 shows a tape drive 10 mounting sequence for tape 21 in cartridge17. At arrow 120 a cartridge loading sequence is initiated by control30. Such sequence may include fetching, indicated by double-headeddashed-line arrow 15, a cartridge from library 14 and transporting it totape drive 10. Step 121 loads cartridge 17 into a play position of tapedrive 10 as diagrammatically shown in FIG. 1. In step 122, sensor 31senses and indicates that cartridge 17 is in the FIG. 1 play positionand supplies the indication to control 30. Control 30, in step 123,actuates tape spools 20, 15 to rotate and a known tape threadingmechanism (not shown) to thread tape 21 past head 27 onto machine spool25. In those cartridges in which both spools are in the cartridge, thethreading step is omitted. Step 124 (control 30 initiated) calibratesthe tape drive 10 servo control (not shown) and read back circuits(notshown) to the tape 21 recording characteristics and the locations ofservo track areas 40-42 in the FIG. 2 illustrated tape 21. Step 130reads FID 60 from tape 21 to determine that tape 21 has a drivepartition having MDI, DBM and SARS as shown in FIG. 2. If step 132 showsthat FID 60 was successfully read, then steps 135 et seq are performed.If FID 60 was not successfully read, then an error condition is signaledrequiring an error recovery that is beyond the present description.

Steps 135-144 constitute an operation loop for finding one valid andreadable DBM and SARS. Step 135 reads MDI N (N=1 in the first pass).Step 136 determines the status indicated in MDI N as being eitherdemounted (correct status) or mounted (error status). If step finds MDIN indicating a demounted status, then step 140 read DBM N and SARS Ninto RAM 33 respectively in areas 34 and 35. Step 141 determines whetherboth DBM N and SARS N have been successfully read. If YES, then step 150causes tape drive 10 to indicate to controller 11, hence other units 12,that the requested volume mount has been completed. Step 151 thenaccesses all copies of MDI 1-K, K is a positive integer, for rewritingeach MDI to reflect status of tape 21 as being mounted.

Returning to decisions step 141, if the read of either DBM or SARSfails, then the NO exit is taken to step 142 for incrementing the loopcount. Step 143 compares the increment count with the maximum number K-1of loop traversals. If the maximum number is exceeded, then an error 144is signaled to other units 12. If the loop count is not greater thanK-1, then the loop is repeated by executing steps 135-143 as justdescribed.

Next, returning to step 136, if MDI N indicates the mount status, thenerror exit (YES) is used. The error is logged in RAM 33 for later use asmay be desired. Then, steps 142 et seq are performed as previouslydescribed.

The described mounting procedure requires but one of the K MDI's toindicate demounted status. For purposes of reliability, availability andserviceability, it may be desired that M of K MDI's have a demountedstatus. M is an integer 0 or greater and not greater than K. Note thatinability to read a given copy of MDI, DBM or SARS does not give rise tothe last-stated alternate procedures. In any event, the separate SARScopy 35 is updated to reflect any of the described error conditions.

FIG. 6 shows a procedure usable to keep the DBM and SARS separate copiesin RAM 33 current. Note that the copies of DBM and SARS on tape 21 arenot updated until demount time shown in FIG. 10. Step 180 receives acommand in tape drive 10 from other units 12 relating to format on tape21. Such commands include a write command that adds data to existingdata resulting in moving any EOD tape control block, creating a newpartition, creating a logical volume and the like. As may be required bythe received command, step 181 writes data on tape 21. Step 182 updatesthe separate DBM copy 34 in RAM 33. Step 186 updates the separate copy35 of SARS in RAM 33. The SARS copy 35 may also be updated independentlyof command execution if either controller 11 or tape drive 10 detect anerror that is a subject of SARS. Step 187 is an optional step forkeeping the tape 21 DBM and SARS copies as current as possible. If tapedrive 10 is not busy, or not busy for some predetermined elapsed time,and tape 21 is positioned at head 27 only a maximum predetermined lengthfrom logical load point in track group 0, then the tape 21 copies of DBMand SARS may be updated. It should be noted that all or none of the tapecopies should be updated at a given instance--all tape copies of DBM andSARS should be identical.

FIG. 7 shows a simplified version of a high speed locate to apredetermined sector. Arrow 190 indicates an initiation of the highspeed block locate. Step 191 moves the tape to a wrap midpoint (DBM copy35 field 95 yields the sector number for any desired wrap midpoint).FIG. 7 assumes that head 27 has been indexed to read tracks from anappropriate track group as determined from partition directory 91, forexample. After head 27 reaches a target midpoint, then step 192 movetape 21 to a so-called landing area this is just "upstream" (in aforward direction would be scanned before a target sector, logicalvolume etc) from a target position. The step 192 may be either a highspeed movement (head 27 does not sense tape 21 recorded data) controlledusing tachometer 22 generated count values or a slow speed movement(head 27 reads the tape 21 recorded data) for finding a block ID orother machine sensible indicium.

FIG. 8 illustrates generating a high speed movement to an end of alldata recorded on tape 21. This operation is caused by a request,represented by arrow 200, from other units 12 to add a new file or otherdata to tape 21. Step 201 reads the EOD directory 97 for identifying thesector or physical location of the last EOD in the directory. Step 202indexes head 27 to the track group in which the last EOD has beenrecorded. Then a high speed locate to the sector for the last EODindicated in directory 97 is performed, such as set forth with respectto FIG. 7.

FIG. 9 illustrates using tape mark directory 92 with respect to filesrecorded on tape 21. Other uses may be easily envisioned. A requestreceived from other units 12 initiates a tape 21 positioning operation.Step 211 reads tape mark (TM) directory 92 for finding the tape markthat defines a trailing extremity of the request identified file. Step212 evaluates the time of head and tape positioning motions required torespond to the received request. Step 214 determines whether or not adistance D of tape motion (after head indexing) is greater than a motionthreshold T for effecting a high speed (non reading) tape motion. Isyes, then step 215 effects a fast or high speed locate to the upstreamfile limit indicated by a first one of the tape mark blocks. Otherwise,step 218 effects a slow speed access to the identified tape mark.

FIG. 10 illustrates demounting tape 21 while leaving tape 21 loaded, butnot mounted, in tape drive 10. Step 160 receives an other unit requestin tape drive 10 to demount tape 21. Such a demount request may beexplicit for tape 21 or implicit by requesting a demount of a logicalvolume on tape 21. Step 161 determines whether tape 21 is in factmounted, i.e. the tape copies of MDI are all indicating mounted status.If not mounted, even though loaded in tape drive 10, line 162 indicatesan error condition that is reported to other units 12. Since this erroris not related to tape 21, no copy of SARS needs to be updated.

Assuming that tape 21 is mounted, then step 164 moves tape 21 to itsload point (rewind tape). Tape drive 10 builds a MDI in RAM 33 thatshows tape 21 is demounted. Then operation loop 165-168 copies theseparate copies of DBM 34 and SARS 35 to tape 21. The MDI status in alltape copies of MDI are changed to demount. Loop 165-168 includes firstcopying the RAM copy of DBM 1 and SARS 1 to tape 21 (see FIG. 2) step166 increment loop counter (not shown). Step 167 compares current loopcount N with K. If N is not greater than K, then step 168 records MDI 1.For reducing tape 21 motion, MDI 1 may be positioned on tape 21 justafter SARS 1 such that all blocks DBM 1, SARS 1 and MDI 1 can berecording in one pass. In any event, loop 165-168 is repeated K times.Step 174 resets the loop counter to one in preparation for a nextdemount. Step 175 writes an new EOD 78. Since data may have been addedto DBM and SARS, the new EOD 78 is moved toward a downstream end of thedrive partition. Tape drive 10 then signals other units 12, viacontroller 11, that the requested volume (whether logical or tape 21)has been demounted. Cartridge 17 with tape 21 remain loaded in tapedrive 10. A reason for leaving tape 21 loaded is that additional dataprocessing activity may occur with respect thereto. Numeral 176indicates intervening data processing activity. Step 178, executed intape drive 10, determines that a different cartridge is to be loaded andprobably mounted in tape drive 10. Step 179 unloads cartridge 17 forreturning it to library 14 and loads and mounts a different cartridge(not shown) in tape drive 10.

FIG. 11 illustrates generating a drive partition and a partition as afirst addressable data-storing partition on tape 21. A scratch tape isloaded into drive 10. Drive 10 attempting to read the tape determinesthat the loaded tape is scratch (not formatted). It is noted that inmany data processing systems, an attaching host will command loading andmounting a scratch tape such that tape drive 10 is expecting the scratchtape. In any event, step 230 verifies that the loaded tape is a scratchtape. It is preferred that the scratch tape has factory recorded servoareas 40-42 and calibration area between dashed lines 50 and 52 (FIG.2). Control 30 then can format the scratch tape by creating in memory 33data for a drive partition that is not addressable by any attaching unit11 or 12. Such data includes the directory structures hereinabovedescribed. Such creation first includes recording patterns incalibrating area developing and recording the BOW and EOW tape controlmarks in the respective track groups. Writing BOW and EOW can bedeferred until data written to tape 21 reaches the respective beginningand ends of the data tracks (wrap ends). The physical locations of suchtape control marks are entered into the wrap point map 95 being built inmemory 33 (DBM 34). A SARS 35 is also built in memory 33. Uponcompleting DBM 34 and SARS 35 plus a mount-demount tape control blockindicating that the loaded scratch tape is not mounted, peripheral drive10 is ready to complete the formatting. Such formatting is completed bycopying and recording all of the data onto the scratch tape beginning ata logical load point in track group 0. Upon completing formatting, theloaded tape has MDI indicating the tape is not mounted and the onlyrecording thereon are the above-mentioned tape control blocks and thedrive partition 60-78. Drive partition 60-78 is not assigned any addressnor sequence number for ensuring that it is addressable only by movingthe formatted tape to load point, then tape drive 10 accessing the datain such drive partition. All other partitions are assigned a number(address) beginning with zero that make such partitions addressable.From step 231 other operations are performed leaving the just-formattedtape loaded in tape drive 10 but not mounted.

Tape drive 10, in step 232 receiving a request from other units 12 toallocate space on a magnetic tape proceeds in step 233 to mount thejust-formatted tape as described with respect to FIG. 4. First, tapedrive 10 in step 236 identifies the physical location of the last EOD.Since the just-formatted tape has only the drive partition, EODdirectory 97 indicates end of data in the just-formatted tape to thedrive partition. Tape drive 10 in step 237 then generates a firstaddressable partition as partition 0 in track group 0 beginning at atrailing end of the drive partition. The length of partition 0 dependson requested data capacity. Tape drive 10 then selects two physicallocations for identifying partition 0. Optionally, an EOD tape controlmark is recorded at the beginning physical location of partition 0 isindicate that the partition is empty. Then, step 238 records thedefinition of partition 0 in partition directory 91 of DBM 34. Partition0 is now ready to receive and store data. Other partitions are similarlycreated, each new partition being assigned a next higher sequencenumber.

Since tachometer 22 defines tape segments, allocation of partition 0 canbe by selecting a number of tape segments beginning at the end of thedrive partition. Adding the number of added segments to the physicallocation indicating the end of the drive partition results in atachometer value indicating the physical location of the end ofpartition 0.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:
 1. A method of recording data onto and reading datafrom a data storage medium wherein a drive supports and provides accessto the storage medium and a host means sends and receives data to andfrom the drive for recording on and reading from the storage medium,said storage medium and a head being relatively movably mounted in thedrive for accessing portions of the record storage medium for recordingdata onto and reading data from the storage medium, including thesteps:establishing a first data storage area on the storage medium,making said first data storage area addressable by said drive and notaddressable by said host means such that the host cannot write data ontonor read data from the storage medium by addressing said storage medium;establishing a plurality of second data storage areas on the storagemedium, making all of said second data storage areas accessible to saidhost by said host addressing said second data storage areas; in saidfirst data storage area establishing a plurality of directories ofpredetermined physical access parameters of said storage medium, in eachof said established directories storing first identifications of dataelements stored in the data storage medium and with each of said firstidentifications storing respective second identifications of physicallocations on said storage medium of said data elements; and in saidsecond data storage areas storing predetermined ones of said firstidentifications of said logical data elements along with storing saidlogical data elements; in said drive, receiving a request from the hostmeans for accessing one logical data element in one of said second datastorage areas; in said drive, before accessing said one of said seconddata storage areas, transferring a copy of a predetermined portion ofone of said directories from the first data storage area to a memoryexternal of the storage medium, then accessing a predetermined one ofsaid directories in said memory for retrieving a predetermined one ofsaid physical locations indicated in said one directory, then in saiddrive relatively moving said head and said storage medium to a saidindicated physical location; in said drive, from said indicated physicallocation relatively moving said head and storage medium in apredetermined direction for accessing said one logical data element insaid one of said second data storage areas for exchanging data betweenthe one data storage area and said drive without further reference toany of said physical location data; recording in each of said seconddata storage areas that stores data an end of data mark that indicatesan end of the stored data in the respective ones of said second datastorage areas; in the drive, recording in said first data storage areaan end of data directory having an identification of all of saidrecorded end of data marks including respective indications for saidrecorded end of data marks indicating respective physical locations onthe storage medium at which said recorded end of data marks are located;and sorting in said end of data directory for listing all of saidrecorded end of data marks in an order in which said recorded end ofdata marks appear in said second data storage areas such that one ofsaid end of data marks indicates an end of data for all data stored inall said second data storage areas.
 2. The method set forth in claim 1,including the steps:receiving in said drive from said host means avolume table of contents for said storage medium; in said host means,including in said volume table of contents a plurality of indicationsrespectively identifying predetermined ones of said second data storageareas and identifications of data contents of said identifiedpredetermined ones of said second data storage areas; and storing saidreceived volume table of contents in a predetermined one or saidpredetermined ones of said second data storage areas.
 3. The method setforth in claim 1, including the steps:selecting said storage medium tobe an elongated magnetic tape having a plurality of data storage trackscannable by said head means by relatively moving said tape and saidhead means; making said tracks extending longitudinally of said tape;and establishing a load point at which said head means is firstrelatively positioned for accessing said first data storage area beforeaccessing any of said second data storage areas.
 4. The method set forthin claim 3, including the steps:in said magnetic tape, establishing aplurality of track groups, establishing in each said track group aplurality of first and second clusters of data tracks, establishing ineach one of said first clusters a forward direction of scanning in afirst relative direction of tape and head means relative motion,establishing in each one of said second clusters said forward directionof scanning in a second direction of relative motion of said magnetictape and said head means that is opposite to said first direction ofsaid magnetic tape and said head means relative motion; establishing ineach said track cluster a predetermined number of physical referencepoints at respective predetermined longitudinal locations on the tape;in said drive, identifying and indicating each said longitudinalreference points of said data tracks in each said track cluster; andestablishing in said first data storage area a map of said referencepoints and recording in said map a predetermined identification of eachrespective location of all of said identified reference points.
 5. Themethod set forth in claim 4, including the steps:in said magnetic tape,determining and indicating for each of said second data storage areasphysical magnetic tape displacement locations of a beginning and end ofeach one of said second data storage areas; and in said first datastorage area creating a partition directory, recording in said partitiondirectory an identification of all said second data storage areas andsaid indicated physical magnetic tape displacement locations of thebeginning and end of each said second data storage areas.
 6. The methodset forth in claim 5, including the steps:receiving in said drive arequest from said host means to access a predetermined one of saidsecond data storage areas; in said drive, determining and indicating acurrent relative position of said predetermined one of second datastorage areas to said head means, determining and indicating a physicallocation of said predetermined one of said second data storage areas; insaid drive, determining and indicating a predetermined one of saidreference points in a predetermined one of said track clusters that hasa relative predetermined displacement from said predetermined one ofsaid second data storage areas; relatively moving said magnetic tape andsaid head means to said predetermined one of said reference points; andfrom said predetermined one of said reference points relatively movingsaid magnetic tape and said head means for enabling the head means toscan said tracks in said predetermined one of said track clusters insaid forward direction to said predetermined one of said second datastorage areas.
 7. The method set forth in claim 6, including thesteps:recording data in said predetermined one of said second datastorage areas; in said drive, after recording data in said predeterminedone of said second data storage areas, recording an end of data mark ata given physical location in said predetermined one of said second datastorage areas; and in said first data storage area, recording said givenphysical location as an end of data in said predetermined one of saidsecond data storage areas.
 8. The method set forth in claim 3, includingthe steps:establishing a memory in the drive; in the drive, copying datafrom said first data storage area to said memory; and recording a markin the first data storage area that indicates the data stored in saidfirst data storage area is invalid.
 9. The method set forth in claim 8,including the steps:making said magnetic tape a removable medium on asupply reel and providing in said drive a magnetic tape receiver andmeans for transporting said tape between said machine reel and saidsupply reel; in said drive, sensing and indicating that said magnetictape is in said receiver; in said drive, indicating that said magnetictape in said receiver is not mounted in the drive; and after saidcopying data from said first data storage area to said memory,indicating that said magnetic tape is mounted in said drive.
 10. Themethod set forth in claim 9, including the steps:receiving in said drivea request from said host means to demount said magnetic tape from saiddrive; copying all of the data stored in said memory to said first datastorage area; recording a second mark in said first data storage areafor indicating that said magnetic tape is demounted and that data storedin said first data storage area is valid; leaving said magnetic tape insaid drive; and indicating to said host means that said magnetic tape isdemounted from said drive.
 11. A method of recording data onto andreading data from a data storage medium wherein a drive supports andprovides access to the storage medium and a host means sends andreceives data to and from the drive for recording on as recorded dataand reading said recorded data from the storage medium, said storagemedium and a head being relatively movably mounted in the drive foraccessing portions of the record storage medium for recording data ontoand reading said recorded data from the storage medium, including thesteps:establishing a first data storage area on the storage medium,making said first data storage area addressable by said drive and notaddressable by said host such that the host cannot write data onto norread data from the storage medium by addressing said storage medium;establishing a plurality of second data storage areas on the storagemedium, making all of said second data storage areas accessible to saidhost by said host addressing said second data storage areas; in saidfirst data storage area establishing a plurality of directories ofpredetermined physical access parameters of said storage medium, in eachof said established directories storing first identifications of dataelements stored in the data storage medium and with each of said firstidentifications storing respective second identifications of physicallocations on said storage medium of said data elements; and in saidsecond data storage areas storing predetermined ones of said firstidentifications of said logical data elements along with storing saidlogical data elements; in said drive, receiving a request from the hostmeans for accessing one logical data element in one of said second datastorage areas; in said drive, before accessing said one of said seconddata storage areas, transferring a copy of a predetermined portion ofone of said directories from the first data storage area to a memoryexternal of the storage medium, then accessing a predetermined one ofsaid directories in said memory for retrieving a predetermined one ofsaid physical locations indicated in said one directory, then in saiddrive relatively moving said head and said storage medium to a saidindicated physical location; in said drive, from said indicated physicallocation relatively moving said head and storage medium in apredetermined direction for accessing said one logical data element insaid one of said second data storage areas for exchanging data betweenthe one data storage area and said drive without further reference toany of said physical location data; in said drive, generating a firstplurality of diverse types of medium control blocks; on said recordingmedium, recording, interleaved with said recorded data, a secondplurality of said medium control blocks at predetermined physicallocations in said storage medium; and in said first data storage arearecording a different one of said plurality of directories forrespectively identifying each said type of medium control blocksincluding indicating said predetermined physical locations in therespective directories for each said medium control block identifiedtherein.
 12. The method set forth in claim 11, including the steps:insaid drive, determining and indicating a plurality of physical relativelocations of said magnetic tape relative to said head means; in saidsecond data storage areas establishing partitions, each of saidpartitions comprising at least one of said second data storage areas,identifying each one of said partition by first respective ones of saidphysical relative locations; and in said first data storage area,establishing a separate directory for said partitions includingidentification of said first respective physical locations and aseparate directory for each type of said diverse medium control marksand including identifications of said second respective physicallocations for each of said medium control marks.
 13. The method setforth in claim 12, including the steps:in the first data storage area,recording a mount one of said medium control blocks including recordingsaid mark in said mount one of said medium control blocks for indicatingthat said magnetic tape is mounted in said drive; in the drive,recording into said first data storage area a copy of said data storedin said memory; and after recording a copy of said data stored in saidmemory into said first data storage area, in the drive, creating aunmount one of said medium control blocks including an indication thatsaid tape is not mounted and that said data stored in said first datastorage area is valid, then recording said unmount one of said tapecontrol blocks in said first data storage area for obliterating saidmount one of said medium control blocks.
 14. The method set forth inclaim 13, including the steps;in the drive, while recording and readingdata on and from said magnetic tape, detecting and indicatingpredetermined errors; in the drive, creating a an error one of saidmedium control blocks, then storing said error one of said mediumcontrol blocks in said memory.
 15. The method set forth in claim 11,including the steps:making first ones of said medium control blocks endof data blocks; after recording data in each said first and secondaddressable data areas, recording one of said end of data blocks; in thedrive, immediately after recording each of said end of data blocks,detecting and indicating a physical location of each said end of datablock; and making one of said directories for identifying all of saidend of data blocks and said detected and indicated physical location ofeach said end of data blocks, link listing said identifications in saidone directory in order of said detected and indicated physical locationsbeginning with an end of data block in said first data storage area. 16.The method set forth in claim 12, including the steps:making first onesof said tape control blocks end of data blocks; making second ones ofsaid tape control blocks tape marks for indicating longitudinalextremities of data files recorded on the tape; after recording in eachsaid first and second addressable data areas recording one of said endof data blocks; in the drive, immediately after recording each of saidend of data blocks, detecting and indicating a physical location of eachsaid end of data block; before and after recording predetermined data inone of said partitions recording a tape mark one of said tape controlblocks and detecting and indicating a tape mark physical location ofsaid recorded tape mark tape control block; making a first saiddirectories for identifying all of said end of data blocks and saiddetected and indicated physical location of each said end of datablocks, link listing said identifications in said one directory in orderof said detected and indicated physical locations beginning with an endof data block in said first data storage area; making a second of saiddirectories for identifying all of said tape mark tape control blocksand said detected and indicated tape mark physical location of each saidtape mark tape control blocks, link listing said identifications in saidsecond directory in order of said detected and indicated tape markphysical locations beginning with an end of data block in said firstdata storage area; in said tape drive, reading one of said first orsecond directories for identifying a predetermined one of saididentified tape control blocks and its associated physical location;then relatively moving said head means and said tape to an out ofcontact relationship at a first relative speed from a current relativeposition to said associated physical location; and then relativelymoving said head means and said tape in a transducing relation.
 17. Amethod of recording data onto as recorded data and reading said recordeddata from a data storage medium wherein a drive supports and providesaccess to the storage medium and a host means sends and receives data toand from the drive for recording on and reading said recorded data fromthe storage medium, said storage medium and a head being relativelymovably mounted in the drive for accessing portions of the recordstorage medium for recording data onto and reading said recorded datafrom the storage medium, including the steps;establishing a first datastorage area on the storage medium, making said first data storage areaaddressable by said drive and not addressable by said host such that thehost cannot write data onto nor read data from the storage medium byaddressing said storage medium; establishing a plurality of second datastorage areas on the storage medium, making all of said second datastorage areas accessible to said host by said host addressing saidsecond data storage areas; in said first data storage area establishinga plurality of directories of predetermined physical access parametersof said storage medium, in each of said established directories storingfirst identifications of data elements stored in the data storage mediumand with each of said first identifications storing respective secondidentifications of physical locations on said storage medium of saiddata elements; and in said second data storage areas storingpredetermined ones of said first identifications of said logical dataelements along with storing said logical data elements; in said drive,receiving a request from the host means for accessing one logical dataelement in one of said second data storage areas; in said drive, beforeaccessing said one of said second data storage areas, transferring acopy of a predetermined portion of one of said directories from thefirst data storage area to a memory external of the storage medium, thenaccessing a predetermined one of said directories in said memory forretrieving a predetermined one of said physical locations indicated insaid one directory, then in said drive relatively moving said head andsaid storage medium to a said indicated physical location; in saiddrive, from said indicated physical location relatively moving said headand storage medium in a predetermined direction for accessing said onelogical data element in said one of said second data storage areas forexchanging data between the one data storage area and said drive withoutfurther reference to any of said physical location data; recording ineach of said second data storage areas that stores data an end of datamark that indicates an end of the stored data in the respective ones ofsaid second data storage areas; in the drive, recording in said firstdata storage area an end of data directory having an identification ofall of said recorded end of data marks including respective indicationsfor said recorded end of data marks indicating respective physicallocations on the storage medium at which said recorded end of data marksare located; sorting in said end of data directory for listing all ofsaid recorded end of data marks in an order in which said recorded endof data marks appear in said second data storage areas such that one ofsaid end of data marks indicates an end of data for all data stored inall said second data storage areas; selecting said storage medium to bean elongated magnetic tape having a plurality of data storage trackscannable by said head means by relatively moving said tape and saidhead means; establishing a load point at which said head means is firstrelatively positioned for accessing said first data storage area beforeaccessing any of said second data storage areas; in said magnetic tape,establishing a plurality of track groups, establishing in each saidtrack group first and second clusters of data tracks, establishing ineach said first cluster of data tracks a forward direction of scanningin a first relative direction of tape and head means motion,establishing in each said second cluster of data tracks said forwarddirection of scanning in a second direction of relative direction oftape and head means motion that is opposite to said first relativedirection of tape and head means motion; establishing in each said trackcluster a predetermined number of physical reference points atrespective predetermined longitudinal locations on the tape; in saiddrive, identifying and indicating each said longitudinal referencepoints of said data tracks in each said track cluster; and establishingin said first data storage area a map of said reference points andrecording in said map a predetermined identification of each respectivelocation of all of said identified reference points; in said first datastorage area, recording a first plurality of copies of each saiddirectories and said mount tape control block; while recording saidfirst plurality of copies, arranging said directory copies and saidmount tape control copies into a predetermined physical relationshipsuch that respective ones of said mount tape control copies arelogically associated with respective ones of said directory copies; inthe drive, after recording said first plurality of copies, reading oneof said copies of each said logically associated mount tape controlblocks and directories and storing the read copy into said memory; andafter said reading step, in said first data storage area, replacing allof said unmount tape control blocks with a first plurality of saidunmount tape control blocks.
 18. A method of recording data onto andreading data from a data storage medium wherein a drive supports andprovides access to the storage medium and a host means sends andreceives data to and from the drive for recording on and reading fromthe storage medium, said storage medium and a head being relativelymovably mounted in the drive for accessing portions of the recordstorage medium for recording data onto and reading data from the storagemedium, including the steps:establishing a directory having firstdirectory contents in a first portion of said storage medium thatindicates physical locations of data blocks stored in said storagemedium; indicating in a first partition that said storage medium is notmounted to said drive; reading a copy of said first directory contentsfrom said first partition into a memory in said drive; then changingsaid indication in said first partition that said storage medium ismounted in said drive and that said directory is not a valid copy of thefirst directory contents in said drive, generating a first plurality ofdiverse types of medium control blocks; recording data onto the recordmedium as recorded data; in said recording medium, interleaving andrecording a second plurality of said medium control blocks among saidrecorded data at respective predetermined physical locations in saidstorage medium; and in said first portion recording a second directoryfor respectively identifying each said type of medium control blocksincluding indicating said predetermined physical locations in the seconddirectory for each said medium control block identified therein.
 19. Themethod set forth in claim 18, including the steps:selecting said storagemedium to be an elongated magnetic tape having a plurality oflongitudinally-extending data storage tracks scannable by said headmeans by relatively moving said tape and said head means; establishing aload point at which said head means is first relatively positioned foraccessing said first portion before accessing any of said second datastorage areas; in said magnetic tape, establishing a plurality or trackgroups, establishing in each said track group first and second clustersof said longitudinally-extending data storage tracks, establishing ineach said first cluster of data tracks a forward direction of scanningin a first relative direction of tape and head means motion,establishing in each said second cluster of data tracks said forwarddirection of scanning in a second direction of relative direction oftape and head means motion that is opposite to said first relativedirection of tape and head means motion; establishing in each said trackcluster a predetermined number of longitudinal physical reference pointsat respective physical longitudinal positions in said each trackcluster; in said drive, identifying and indicating each saidlongitudinal reference point of said data tracks for each said trackcluster; establishing in said first portion a map of said trackreference points and recording in said map all of said identifiedreference points; in said tape, establishing a plurality of addressablepartitions, detecting and indicating for each said addressable partitiona physical location in one of said track clusters of a beginning end ofeach said partition; and in said first portion creating a partitiondirectory, recording in said partition directory an identification ofall said established partitions and said indicated respective physicalmagnetic tape displacement locations of the beginning each saidpartitions.
 20. Apparatus for recording data onto and reading data froman elongated magnetic tape data storage medium, said data storage mediumhaving a plurality of elongated data-storing tracks, a drive supportingand providing access to the data storage medium, host means sending andreceiving data to and from the drive for recording data on as recordeddata and reading said recorded data from the data storage medium, headmeans being relatively movably mounted in the drive for relativemovements with respect to said data storage medium for accessing saidelongated data-storing tracks for relatively scanning said tracks of thedata storage medium for recording said data onto and reacting saidrecorded data from said data-storing tracks, including incombination:tachometer means operatively connected to said data storagemeans for metering relative movements of said data storage means andsaid head means for indicating relative successive physical positions ofsaid head means and said data storage medium; first partition meansconnected to said tachometer means for establishing a first partition onthe storage medium and for designating said first partition a drivepartition for making said first partition addressable only by saiddrive; second partition means connected to said tachometer means forestablishing a plurality of second partitions on the data storagemedium; indicating a respective one of said relative physical positionsas a beginning of said partitions, address means in said secondpartition means for assigning addresses to each of said secondpartitions for enabling host and drive addressable access to said secondpartitions; medium map means connected to said first and secondpartition means for establishing and maintaining in said first partitiona plurality of directories of predetermined physical access parametersof said storage medium including storing first identifications of dataelements stored in the partitions of the data storage medium and witheach of said first identifications storing respective indications ofsaid relative physical locations on said storage medium; said datastorage medium having a plurality of track groups, each said track grouphaving a plurality of first and second track clusters, said data-storingtracks in each one of said first track cluster having a forwarddirection of scanning in a first relative direction of tape and headmeans movement, data-storing tracks in each one of said second trackclusters having said forward direction of scanning in a second directionof relative direction of tape and head means motion that is opposite tosaid first relative direction of tape and head means motion; each saidtrack cluster having a predetermined plurality oflongitudinal-position-indicting indicating reference points respectivelyat predetermined longitudinal locations in said data storage medium;said tachometer means including point means for identifying a physicallocation of each said reference points; said directory means connectedto said point means for storing a predetermined indication of all ofsaid identified reference points in one of said directories; medium markmeans in said drive for generating and reading a plurality of diversetypes of medium marks, mark recording means in said medium mark meansfor recording diverse ones of said medium marks on said data-storingtracks in said track clusters, respectively, interleaved with saidrecorded data; cluster means in said medium mark means for recordingbeginning and ending wrap medium marks for indicating respectively abeginning and an end of each of said clusters; end of data means in saidmedium mark means for recording an end of data medium mark in each ofsaid partitions that are storing a portion of said recorded data andindicating a physical location of each of said end of data medium marks;and directory means connected to said end of data means for sorting saidend of data medium marks in accordance with said physical locationindication of each said end of data medium mark for created a sortedlist of said end of data medium marks for indicating a predetermined oneof said end of data medium marks as indicating an end of data for saiddata storage medium.
 21. Apparatus set forth in claim 20, furtherincluding:mount control means connected to the storage medium fordetecting and indicating presence of said storage medium in the drive; amemory; directory means connected to the memory and to the data storagemedium for reading data from said first portion into said memory; saidmount control means having status means connected to said directorymeans and to said data storage medium for responding to said directorymeans copying said data from said first portion to said memory forrecording in said drive partition an indication that said data storagemedium is mounted into said drive and that said memory copy of saiddirectories is an only valid copy of said directories.
 22. Apparatus setforth in claim 20, further including;partition accessing means connectedto said one directory for relatively moving said head means and saiddata storage medium in a non-contact high speed movement to apredetermined one of said reference points and then relatively movingsaid head means and said data storage medium in a transducingrelationship from said predetermined one of said reference points insaid forward direction to a given predetermined one of said partitionsfor accessing said given predetermined one of said partitions. 23.Apparatus set forth in claim 22, further including:demount meansconnected to the data storage medium, to said memory and to saiddirectory means for actuating the directory means to copy saiddirectories from said memory to said drive partition and connected tothe magnetic tape to record in said drive partition an indication thatsaid magnetic tape is demounted from the drive and that said copieddirectories in said drive partition are an only valid copy of saidcopied directories.
 24. The apparatus set forth in claim 20, includingin combination:said medium map means having given means for recording afirst plurality of copies of each said directories and said mount tapecontrol block; sort means in said medium map means while said givenmeans is recording said first plurality of copies, arranging said firstplurality of said directory into a predetermined physical relationshipin said first partition.